937
FXUS61 KCTP 051911
AFDCTP

Area Forecast Discussion
National Weather Service State College PA
311 PM EDT Wed Aug 5 2026

.WHAT HAS CHANGED...

*No significant changes at this time.

&&

.KEY MESSAGES...
1) Trending more humid with heavy downpours and localized flash
flooding possible late this week into the weekend

2) Severe thunderstorms are possible Thursday and Friday
afternoons/evenings

3) Heat index could approach 100F Thursday and Friday SE of
Harrisburg

&&

.DISCUSSION...
KEY MESSAGE 1: Trending more humid with heavy downpours and
localized flash flooding possible late this week into the
weekend

Weak sfc low (1018 MB) near KDCA, with an ill-defined warm
front extending NE along the I-95 corridor and an inverted
trough into the Lower and Middle Susq Valleys will be the focus
for several waves of heavy showers and a few TSRA through early
tonight, while another sfc low(s) (1017 MB) over Central and
Southern Ohio will bring similarly slow-moving and training
showers/and a few TSRA, mainly west of the RT 219 corridor.

12 hour POPS across our Laurel Highland zones will be 60-70% and
in 70-80+% range across the Lower Susq Valley.

Most of the CWA is in WPC`s MRGL risk of Excessive Rainfall
(Flash Flooding) for the next 5 days (with the entire state in a
MRGL risk for Fri and Sat).

We expect PWATS to climb to +1-2 Sigma with corresponding sfc
dewpoints rising into the 70s over the S and U60s in the N and
stay there right through at least Tuesday.

PWATs seem to peak this afternoon around 2.25" in the SE. Then
they don`t get that high again (daily peaks of 2" in the SE, but
1.7" in the NW). A pattern shift to a more- zonal flow aloft
should occur over the weekend, but a cold front and/or dry air
is not in store for us.

The confidence in flooding is low due to confidence in
placement of the heaviest rain being low. Certainly, the wettest
places from over the weekend will sit higher on the list, and
there are some hints that the SErn third or so of the area will
be most at- risk for repeated shots of heavy rain. But, no flood
watch are expected for today, and we`ll only get a better feel
for each new day as we see where the previous day`s precip has
been heaviest.

   ------------------------------------------------------

KEY MESSAGE 2: Severe thunderstorms are possible Thursday and
Friday afternoons/evenings

MRGL risk for severe wind gusts exist on Thurs (and likely
Friday, too) over the SE half of the area per the latest SPC
outlooks (new DY3 not out at press time). The shear is less than
modest, but CAPE does climb into the 1000-2000 J/kg each of
those aftns. However, the CAPE is long/skinny, which is more
indicative of heavy rain threat. If we can get some dry air in
the mid levels either day, and the small height falls on Friday
can help jack up the instability and DCAPEs, any of our storms
could make a strong to severe gust.

   ------------------------------------------------------

KEY MESSAGE 3: Heat index could approach 100F Thursday and
Friday SE of Harrisburg

The heat index does get very close to and may exceed 100
degrees across a small portion of our SE zones using the
current NBM guidance temps/dews. However, clouds and the anticipated
showers/storms will keep the HI lower - even if just a degree
or two which would make the difference in advy/no. The temps
won`t be all that abnormal, it will be the dewpoints which would
take us over. At this point, we`ll hold off on heat advisories.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
Surge of low level moisture from south to north will likely
bring mainly MVFR ceilings across the Lower Susq Valley and
points east for the rest of the daylight hours, where low level
convergence zones associated with weak troughs (and a warm
front near the I-95 corridor will combine with the highest
Precipitable Water values to focus lower convective cloud bases.

Cigs most likely trend back to higher end MVFR to low-end VFR
for the late afternoon across the Laurel Highlands. Best odds
for a brief heavy downpour and localized MVFR/IFR visibility
appears to be in the KMDT/KLNS vicinity.

Confidence is generally low regarding precip trends, but
locations from KAOO to KUNV and KIPT should stay predominantly
dry through much of the late afternoon/evening hours. Humid and
stagnant airmass tonight suggests lowering flight cats toward
MVFR with areas of IFR into early Thursday morning.

Outlook...

Thu-Sun...Pockets of fog in the morning. Scattered showers/isolated
t-storms with heavy downpours and localized restrictions.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

WHAT HAS CHANGED...Lambert/Dangelo
KEY MESSAGES...Lambert/Dangelo/Steinbugl
DISCUSSION...Lambert/Dangelo/Steinbugl
AVIATION...Lambert/Steinbugl